Researchers believe they have discovered a rock carving in New Mexico’s Chaco Canyon that represents a total eclipse that occurred more than 900 years ago. The engraving, known as a petroglyph, shows a circle with curved, intricate swirling emissions issuing from it. Around the circle, believed to depict the sun, human figures can be seen in different positions and engaged in different activities.

University of Colorado Boulder Professor J. McKim Malville has said the circle shown in the rock art represents the sun’s outer atmosphere, known as its corona, with the tangled, looped protrusions on its edges dating it to a total eclipse that occurred in the region on July 11, 1097.

Malville made the observation Wednesday to mark the upcoming total solar eclipse on August 21 that will be visible across a large swathe of the U.S.

"To me it looks like a circular feature with curved tangles and structures," Malville said. "If one looks at a drawing by a German astronomer of the 1860 total solar eclipse during high solar activity, rays and loops similar to those depicted in the Chaco petroglyph are visible."

"It turns out the sun was in a period of very high solar activity at that time, consistent with an active corona and CMEs," the pair said in their 2014 paper on the rock art in the Journal of Mediterranean Archaeology and Archaeometry.

The two used several sources to assess the activity of the sun around the time of the 1097 eclipse. The data they gathered included information ancient tree rings from which they could detect the activity of cosmic rays. They also used records of naked-eye observations of sunspots, which go back several thousand years in China. A third method involved looking at historical data compiled by northern Europeans on the annual number of so-called "auroral nights," when the northern lights were visible, an indication of intense solar activity.

The rock carving was first discovered in 1992 by Malville and then-Fort Lewis Professor James Judge and was carved by early Pueblo people. Chaco Canyon, a centre of Pueblo culture in the Southwest a thousand years ago, is believed by archeologists to have been populated by several thousand people and held political sway over an area twice the size of Ohio.